Nettle Contraindications

Stinging nettle is a perennial plant with needle-like hairs on the leaves. These leaves cause intense irritation and stinging when they come in contact with the skin. Both the leaves and the roots of the plant are used in herbal medicine, with each part being used for different purposes. It has been used medicinally for hundreds of years for conditions such as seasonal allergies, arthritis, hives and enlargement of the prostate. As with all herbs, it is important to ensure use of this herb will not interfere with any medications you are taking or produce an undesirable result with certain health conditions.

Pregnancy

• Though nettle is frequently used in pregnancy teas and herbal supplements as a nourishing tonic, empirical evidence supports steering clear of nettle during pregnancy because it can stimulate blood flow to the uterus and pelvic area; it can also stimulate menstruation. Nettle is considered an abortifacient, meaning it has the potential to contribute to the miscarriage of a pregnancy.

Non-Steroidal Anti-Inflammatory Drugs (NSAID)

• In a study of arthritis patients published by Chrubasik et al. in a 1997 issue of "Phytomedicine," nettle enhanced the effect of the NSAID diclofenac. The enhancing effect made 50 mg of diclofenac provide the equivalent of 200 mg in pain reduction. It is possible that this additive effect will be encountered with other NSAIDs. Although this appears to be a positive side effect, your physician should be consulted before taking nettle in conjunction with NSAIDs

5-Alpha-Reductase Inhibitors

• Benign prostatic hypertrophy, or prostate enlargement (BPH), is often treated with a 5-alpha-reductase inhibitor. Caution is advised when taking nettle in conjunction with the 5-alpha-reductase inhibitor finasteride due to possible additive effects. Other herbs commonly used in the treatment of BPH -- saw palmetto and pygeum -- may have additive therapeutic effects with nettle.

High Blood Pressure

• It is believed that nettle may thin the blood. Therefore it is important to avoid its use while taking blood thinning medications such as warfarin or aspirin. Nettle may also lower blood pressure and interfere with the clotting ability of blood, increasing the effects of blood pressure medications such as ACE inhibitors, beta blockers and calcium channel blockers.

Bleeding Disorders

• Nettle may increase risk of bleeding; as a result, caution is advised if you are taking a drug that increases the risk of bleeding or you have a bleeding disorder. Other herbs that increase bleeding -- particularly gingko biloba, garlic and saw palmetto -- should be used with caution when taking nettle.

Allergic Hypersensitivity

• Nettle root often relieves pain when applied directly to stiff or painful joints. Because local contact with the leaves causes irritation, external application of nettle leaves is not recommended. Additionally, if you are hypersensitive or have allergies to nettle or the Urticaceae family, external application should be avoided.

Diabetes

• Blood glucose levels may increase with stinging nettle use if you are diabetic. Monitor your blood sugar very closely and consult with your physician before taking nettle in conjunction with your diabetes medication. Taking nettle along with herbs or other dietary supplements that increase blood glucose levels may require an adjustment in medication dosage.

Diuretics

• Stinging nettle is considered a diuretic---removes water from the body---consequently it may increase the effect of diuretic drugs and promote dehydration. Nettle may increase the excretion of potassium, making it important to eat potassium-rich foods such as bananas, dried apricots, cantaloupe, and spinach when taking nettle. Sodium levels should also be monitored as nettle has a synergistic diuretic effect and may cause excessive sodium loss. Swelling of the body tissues, or edema, is often treated with a diuretic. Nettle is contraindicated when edema is caused by heart disorders or kidney insufficiency. Nettle may act synergistically with other diuretic herbs like horsetail, celery seed, dandelion leaf and elder flower.